Field of the Invention
The present invention relates to an image pickup apparatus that performs auto-focusing based on an output signal from an image pickup element.
Description of the Related Art
Conventional focus detections include a focus detection (image pickup plane phase difference AF) by an image pickup plane phase difference detection method that performs a focus detection by a phase difference detection method based on a focus detection signal, and a focus detection (contrast AF) by a contrast detecting method based on a contrast value of an image signal.
U.S. Pat. No. 4,410,804 discloses an image pickup apparatus including a two-dimensional image pickup element in which one micro lens and a plurality of divided photoelectrical convertors are formed for each pixel. The image pickup apparatus of U.S. Pat. No. 4,410,804 calculates a correlation amount from a focus detection signal output from a pixel (focus detection pixel) having each divided photoelectrical convertor, and calculates an image shift amount from this correlation amount, thereby performing a focus detection by the phase difference detection method.
Japanese Patent Laid-open No. 2013-25246 discloses an image pickup apparatus that performs a focus detection by the phase difference detection method and a focus detection by the contrast detecting method based on the contrast value. The image pickup apparatus of Japanese Patent Laid-open No. 2013-25246 performs the focus detection by the phase difference detection method up to the vicinity of an in-focus position, and then performs the focus detection by the contrast detecting method based on the contrast value.
However, the image pickup apparatus disclosed in Japanese Patent Laid-open No. 2013-25246 may start a focus detection operation in a direction opposite to a direction toward an object outside a detectable defocus range because it first performs the focus detection by the phase difference detection method. As a result, a fast focus detection operation is prevented, and a photo opportunity (scene that a photographer wants to photograph) may be missed. Furthermore, the focus detection operation starting in the direction opposite to the object degrades an operation quality.
On the other hand, an image pickup lens needs to be driven to determine the direction by the contrast AF like a wobbling control, which may cause degradation of the operation quality such as an image blur and an image shake due to image magnification variation.